This invention relates to a magnetic head which uses a shunt biasing magnetoresistive element having a shunt film for applying a transverse biasing magnetic field, and more particularly to a magnetoresistive magnetic head suitable for reading a high-density magnetic recording medium.
As the materials for the shunt film, the conventional shunt biasing magnetoresistive heads use Ti, Ta, Mo, Au Nb or the like as described in the U.S. Pat. Nos. 3,940,797 and 4,663,684 or Zr as described in the Japanese Patent Application Laid-Open No. 128015/1987 (corresponding U.S. patent application Ser. No. 936,617).
In the conventional shunt biasing magnetoresistive head using Ti (titanium), when the temperature rises above 175.degree. C., a reaction occurs between the Ni-Fe alloy (referred to as permalloy hereafter) film formed on the substrate and Ti, deteriorating the characteristic of the permalloy film as a magnetoresistive film. Manufacture of the head requires a variety of processes. There are some processes that can be desirably carried out at temperatures of 175.degree. C. or higher, such as a conductor film forming process, an insulating film forming process and a shielding film forming process. However, there is a problem that to limit the characteristic deterioration of the head, those processes requiring the temperature of 175.degree. C. or higher cannot be used. A Ta (tantalum) film has a high temperature of 350.degree. C. at which the reaction between Ta film and permalloy film starts, but it has a low corrosion resistance compared with the permalloy and Ti. Also, it has an extremely high electrical resistivity of 90 to 200 .mu..OMEGA.cm and thus is not appropriate for the shunt film. When the magnetoresistive film is formed of permalloy, the electrical resistivity of the shunt film should preferably be almost equal to or up to 5 times that of the permalloy film, i.e., 20 to 100 .mu..OMEGA.cm. A smaller value is of course desirable. The above permalloy is an alloy of 7-27 wt % Fe and Ni and often used for the magnetoresistive film. An Mo film also does not react with the permalloy film up to 400.degree. C., but its corrosion resistance is very bad. An Au film reacts with the permalloy film at a low temperature of 150.degree. C. and thus poses a similar problem like that of the Ti film. In the heads which use Zr as a shunt film, the temperature at which the reaction with permalloy film starts increases to 325.degree. C., which is, however, still low considering the temperatures of various other processes for making heads.
In the above conventional techniques, the Nb film used as a shunt film is formed by the sputtering method. Drawbacks of the shunt film thus formed include a very high electrical resistivity of 90 to 200 .mu..OMEGA.cm, a poor corrosion resistance and a tendency of easily reacting with the permalloy film. The Nb film formed by the conventional technique is therefore not suited for the shunt film.
As described above, the shunt films so far known are not satisfactory. Information on the current situation of the technical field of this invention may be gained from the U.S. Pat. No. 3,864,751.